When you've posted an entry to the community, your successful post page will show you an option for editing the entry tags. Click on that, and your entry will pop up. Underneath it, you'll see a long list of tags you can use to describe your entry. You choose the tags by clicking on them; hold down the control key to click on multiple choices. You can do this long after you've posted, too - if you wanted to tag every entry you've ever made in this community (or any other), you can simply go through your entries and click on the edit tags icon next to the edit entry icon.
When you want to ask questions about tips, techniques, or particular recipes, you can go to the community's Recipe Index & FAQ by clicking on the link at the top of the page, or by clicking on the relevent tags at the right-hand side of the page. You can also go to the community info page by clicking on the link at the top of the page to read the community guidelines and use the community search engine.